I'd say christianity doesn't need to be true. The whole point of having faith gets negated by the search for absolute certainty.

Try Kierkegaard and his idea of a "leap of faith".

Not christian myself but applying principles to your life and act "as if" there is a god, then your days until death will be more likely to be like heaven than hell.

I wouldn't oversimplify by just living by principles. Look at the core values of christianity and compare them to something like humanism and you will find common denominators. Some examples: unconditional love, solidarity, generosity, justice and equality, tolerance etc.

Now you could argue: wait actual christians aren't [insert life-affirming value] at all! That is because core principles and values don't seem to be internalized and applied that much, instead the focus lies on finding out if the scripture is true in a scholastic and calculated sense. Roger Bacon criticised this.

In pragmatic terms the bible doesn't need to be true for it work.